<template>
    <div class="pagination">
       
        <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
        <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
        <button v-if="startNumAndEndNum.start > 2">···</button>

        <button v-for="(page,index) in startNumAndEndNum.end" :key="index" v-if="page>=startNumAndEndNum.start" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{page}}</button>


        <button v-if="startNumAndEndNum.end < totalPage -1" >···</button>
        <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo==totalPage}">{{totalPage}}</button>
        <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>

        <button style="margin-left: 30px">共 {{total}} 条</button>
        
    </div>
</template>

<script>

export default {
    name: "Pagination",
    props: ["pageNo", "pageSize", "total", "continues"],
    
    computed: {
        //总共多少页
        totalPage() {
            //向上取整
            return Math.ceil(this.total / this.pageSize)
        },
        //
        startNumAndEndNum() {
            const { continues, pageNo, totalPage } = this;
            let start = 0,
                end = 0;
            //不正常现象【总页数没有连续页码多】
            if (continues > totalPage) {
                start = 1;
                end = totalPage;

            } else {
                //正常现象【连续页码5，但是你的总页数一定大于五】
                //开始数字
                start = pageNo - parseInt(continues / 2);
                //结束数字
                end = pageNo + parseInt(continues / 2);
                //把出现不正常的现象【start数字出现0或负数】纠正
                if(start < 1){
                    start = 1;
                    end = continues;
                }

                //把出现不正常的现象【end数字大于总页码】纠正
                if(end > totalPage){
                    end = totalPage
                    start = totalPage - continues + 1
                }


            }
            
            return{start,end}
        }
    },
   
}

</script>

<style lang="less" scoped>
.pagination {
    text-align: center;

    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
}
.active{
    background: skyblue;
}
</style>